Vaporizing fire extinguisher fluid



United States Patent 9 Keith H. Birkett, Hickman Mills, Mo., assignor toSuperior Products Company, Kansas City, Mo., a corporation of MissouriNo Drawing. Application September 7, 1956 Serial No. 608,431

2 Claims. (Cl. 252-8) This invention relates to fire extinguisher fluidsand refers more particularly to fire extinguisher fluids particularlyadapted to be employed in glass bulb vaporizing fire extinguishers.

It is generally'assumed thatthe effect of fire extinguishing agents canbe explainedon the basis of the following actions:

(1) Cooling action, which lowers the temperature of the combustiblematerial below its ignition temperature.

(2) Blanketing action, which prevents air from reach ing the fire andresults in the dilution of the oxygen content of the surroundings.

(3) Mechanical action, which results from directing the agent across thefire with sufiicient force to cut the flame away from the combustiblematerial.

Studies in the recently developed field'of chemical kinetics alsoindicate that certain substances are capable of exerting an inhibitingeffect in the combustion reactions. This chemical action is notcompletely understood and has not yet been extensively utilized in thesearch for better fire extinguishing agents.

Cooling action is a function of the physical properties of the agent,that is, heat capacity, thermal conductively, and the heat ofvaporization will be of different magnitude for different agents. Thecooling action obviously is also a function of the amount of agent em-2,897,151 Patented July 28, 1959 fire extinguishing fluids notcontaining carbon tetrachloride for use in glass bulb vaporizing fireextinguishers.

Another object of the invention is to provide fire extinguishing fluidsnot containing carbon tertrachloride for use in glass bulb vaporizingfire extinguishers, which fluids have greater efiiciency asextinguishing agents than carbon tetrachloride.

Another object of the invention is to provide fire extinguishing fluidsnot containing carbon tetrachloride for use in glass bulb vaporizingfire extinguishers, which fluids have far less toxicity than carbontetrachloride when pyrolyzed in quenching a fire.

Another object of the invention is to provide such fire extinguishingfluids which have very high blanketing action whereby to prevent airfromreaching the fire and diluting the oxygen content of the surroundingarea i of the fire..

ployed. With most extinguishing agents, except water and highlycompressed carbon dioxide, the amounts are small and the cooling actionis of only secondary importance.

Since the glass bulb type of fire extinguisher does not give themechanical action, it therefore must depend solely upon the blanketingaction of the fluid.

Previous studies have indicated that some halogenated hydrocarbons aresuitable materials for use in the glass bulb type fire extinguisher. Incommercial and industrial as the agent of choice in glass bulb type fireextinguishers. Carbon tetrachloride, while possessing a certain amountof usefulness as a fire extinguisher fluid, has less efliciency than isdesired as an extinguishing agent in its blanketing action and also isundesirably toxic in use. Carbon tetrachloride produces much largerquantities of phosgene and decomposes at lower temperatures than otherchlorinated hydrocarbons. In the inventive extinguisher fluids to beherein disclosed certain compounds employed therein produce hydrogenchloride when pyrolyzed which acts as an olfactory warning agent longbefore enough phosgene forms to become dangerous. Carbon tetrachloridedoes not form hydrogen chloride on heating before the phosgene reachesthe dangerous level. When pyrolyzed, carbon tetrachloride was at aminimum six'times more toxic than any of the compounds employed in theinventive extinguisher fluids. This condition would occur during a firesince the liquid would often fall on a hot surface and be pyrolyzed,giving off toxic fumes.

, use, previously, carbon tetrachloride has been employed Therefore, anobject of the invention is .to provide Another object of the inventionis to provide fire extinguishing fluids as described which will producehydrogen chloride in quantities to provide an olfactory warning agentbefore enough phosgene has formed to become dangerous. 7

Another object of the invention is to provide fire extinguishing fluidsas described having a relatively low cost compared to conventionalextinguishing fluids including carbon tetrachloride.

Another object of the invention is to provide fire extinguisher fluidsas described which have a relatively high Maximum allowableconcentration (the upper limit of concentration of a compound in the airwhich will not cause injury to an individual exposed continuously duringa working day and for indefinite periods of time) relative carbontetrachloride.

Another object of the invention is to provide a fire extinguishing fluidas described having a relatively high protected volume" (the vaporvolume generated at 200 F. divided by the inflammability peak percentageexpressed as a decimal fraction-carbon tetrachloride having a protectedvolume of 392 cubic feet per gallon and a higher value being desired inan improved extinguishing fluid).

Another object of the invention is to provide fire extinguishing fluidsas described having extremely low freezing points (below 30 F.).

Other and further objects of the invention will appear in the course ofthe following description thereof.

Maximum allowable concentration of vapors A useful concept in evaluatingfire extinguishing fluids is the maximum allowable concentration?(M.A.C.). This is defined as the upper limit of concentration of acompound in the air which will not cause injury to an individual exposedcontinuously during a working day and for indefinite periods of time. Insetting the M.A.C. from field studies and animal experiments, certaincriteria are usually followed:

(1) Illness due to intoxication should not result from continuedexposure to the M.A.C.

(2) Marked discomfort to a majority of workers should not result fromcontinuous exposure to the M.A.C.

(3) The M.A.C. should not exceed one tenth the concentration dangerousfor a single exposure of one hour.

(4) Where only animal experimental data is available, the M.A.C. shouldnot exceed one fifth the concentration found to effect animals seriouslyon continued exposure.

A concentration of 2.5 times the M.A.C. should fail maximum allowableconcentrations are useful guides in assessing the relative toxic hazardsof various materials on a quantitative basis.

Liquid volume Liquid volume in ml.

(M.A.C. in D.P.M.) Xmoleeular weight (.86 cu. ft./g. mol specificgravityX 1,000) The liquid volume calculation for carbon tetrachlorideis 2.8. Once again, a much greater value is desired in a fireextinguisher fluid.

Protected volume The protected volume term is calculated from theinflammability peak and the vapor volume generated at 200 F. It iscomputed by dividing the vapor volume generated at 200 F. by theinflammability peak percentage (expressed as a decimal fraction). Carbontetrachloride has a calculated protected volume of 392 cubic feet pergallon. A higher value is desired in an improved extinguishing fluid.

Empirical extinguishing number A 2.8 cubic foot (22.4 liters) steelkettle fitted with a Lucite top was used in experiments to compareextinguisher fluids. The material to be tested was dropped in through athistle tube into a dish in the container. A circulating fan which hadbeen placed in such a position as to blow onto the dish was then turnedon to evaporate the liquid. An inflated vinyl plastic bag within thekettle was allowed to deflate through a tube to the atmosphere whichcompensated for the expansion of the liquid when vaporized and mixed.The vinyl bag was then slowly inflated again and the displaced vapor inthe kettle was passed out through a one inch hole into a 3" x 14"cylinder. In the center of the cylinder was placed a burning cigarettelighter. If the fire extinguisher fluid concentration was too high, theflame of the lighter would be extinguished. The quantities of each fireextinguisher fluid added to the tank were varied until there was only adilference of one ml. between the point of burning and the point ofextinguishing. The volume of liquid required to extinguish the flamevaried for each extinguishing agent. This volume was termed theempirical extinguishing number. This figure is useful since it shows therelationship between extinguishing agents and the relative amountsrequired to put out a fire.

Olfactory warning agents Carbon tetrachloride produces larger quantitiesof phosgene and decomposes at lower temperatures than other chlorinatedhydrocarbons. Since chlorinated ethanes, having at least one hydrogenatom, form hydrogen chloride more readily than chlorinated methanes,which acts as an olfactory warning agent long before phosgene has formedin sutficient quantity to become dangerous, it was desirable to includeat least one chlorinated ethane which would not increase the toxicity orcost or lower the extinguishing ability of the fluids.

Practical extinguishing tests The most positive method for obtaininginformation on the fire extinguishing eflectiveness of differentsubstances is obviously by direct application to test fires.

4 Consequently, a 512 cubic foot shed was built to evaluate theextinguisher fluids.

Paper towels soaked in kerosene and placed in trays were used as thetest fires in the shed. A tray 3 x 3' was selected for use from severalsizes studied. The amount of kerosene was varied to determine the amountnecessary to maintain the flame throughout the test. After many trials,two quarts of kerosene were found to be the most suitable for thestandard fire.

In a test of this nature, it is diflicult to compare the extinguishingability of several difierent fluids. In order to compare carbontetrachloride with other fluids it was necessary to adjust conditions inthe shed so that carbon tetrachloride would not function properly allthe time. This should mean that some of the time it would take a longtime to put out the fire and other times it would not put it out. Theoptimum would be for it to function 50 percent of the time. By doingthis fluids which were assumed to be more efiicient could be tested. Theefficiency could be shown by less time required to put out the fire andby a greater percentage of trials that put out the fire.

To establish these conditions, various means were used which dealtprimarily with varying the ventilation in the shed. At first this wasdone by cutting various sized holes in the shed wall, some openeddirectly and some covered with baffles, but since the wind velocity wasnot constant, reliable data could not be obtained. Ultimately, a blowersystem was established which allowed a constant amount of air into theroom. Two 4 x 4" exhaust portals were cut in the opposite walls.

In order to arrive at a true value it was necessary to run numerousexperiments on the fluids and statistically evaluate their ability toput out a fire.

In the testing procedure, the extinguisher was hung from the ceilingdirectly over the tray. The kerosene and paper towels in the tray werelighted, the doors Closed and the blower turned on. The time at whichthe plunger was released and broke the bulb could be heard. This usuallytook about 40 seconds. The condition of the fire on the test shed wasdetermined by the use of four thermo couples placed over the fire andconnected to a pyrometer on the outside of the building. The temperatureof the fire could then easily be followed and the point at which thetemperature suddenly dropped showed when the fire was out. The resultsof the final practical test showed that carbon tetrachlorideextinguished 52 percent of the fires and the inventive compoundsextinguished from 72 to percent of the fires.

It is evident from careful studies that rarely is it a single ingredientthat puts out a given fire. Usually the action is a combination ofsynergistic effects provided by the various materials in the fluid.Flame studies have indicated that parts of a given fire have differentintensities of flame therein. Each chlorinated or halogenated materialreacts in a diflerent manner to each type of flame.

A fire extinguishing compound composed of trichloroethylene,perchloroethylene and either chlorobromo methane or ethylene dibromidewas formulated which had a greater maximum allowable concentration, agreater liquid volume, a greater protective volume, a lesser empiricalextinguishing number and a greater percentage of extinction in thepractical extinguishing tests than carbon tetrachloride. A specificexample of such a compound including chlorobromo methane consisted of,by volume, 40 percent perchloroethylene, 40 percent trichloroethyleneand 20 percent chlorobromo methane. This example has an empiricalextinguishing number of 8.0, a liquid volume of 19.5, a protected volumeof 564 cubic feet, and a relatively low cost at present prices. Aspecific example of such a compound employing ethylene dibromideconsisted of, by volume, 41) percent trichloroethylene, 40 percentperchloroethylene and 20 percent ethylene dibromide. This specificethylene dibromide also cent trichloroethylene, 25

protected volume of example has an empirical extinguishing number of9.0, a liquid volume of 18.4, a protected volume of 538 cubic feet, and,again, a relatively low cost at present prices. In such a fireextinguishing compound composed of trichloroethylene, perchloroethylene,and either chlorobrorno methane or ethylene dibromide, the percentage byvolume of ethylene dibromide or chlorobromo methane should not be lessthan percent. The percentage by volume of chlorobromo methane orpreferably should not exceed 30 percent. The percentages by volume ofperchloroethylene and trichloroethylene are preferably substantiallyequal.

The addition of methylene dichloride to a fire extin'guishing compoundcomposed of trichloroethylene, perchloroethylene and a member of thegroup consisting of chlorobrorno methane and ethylene dibromide gave asubstantially greater toxicity margin over carbon tetrachloride than thecompound without methylene dichloride. It should be understood, however,that the toxicity of the inventive fluid without methylene dichloride isfar less than carbon tetrachloride itself. A specific example of theinventive fire extinguisher fluid employing methylene dichloride andchlorobrorno methane consists in, by volume, 25 percenttrichloroethylene, 25 percent perchloroethylene, 25 percent methylenedichloride and 25 percent chlorobrorno methane. This compound has anempirical extinguishing number of 8.0, a liquid volume of 21.5, aprotected volume of 553, and relatively low cost at present prices. Aspecific example of the inventive fire extinguisher fluid employingethylene dichloride and ethylene dibromide consists, by volume, of 25perpercent perchloroethylene, 25 percent methylene dichloride and 25percent ethylene dibromide. This compound has an empirical extinguishingnumber of 7, a liquid volume of 21.1, a protected volume of 500 and,again, relatively low cost at present prices. It is feasible to vary thepercentages of the components of the fluid somewhat in the fluidcontaining methylene dichloride. Preferably, the percentage by volume ofperchloroethylene, methylene dichloride and trichloroethylene incombination does not exceed 90 percent. Preferably, also, the percentageby volume of value as to the relative eificiency as extinguishingagents. The empirical extinction numbers of the fluids vary fromapproximately 8 to 50 percent below carbon tetrachloride. This wouldindicate that it would take 8 to 50 percent more carbon tetrachloride toput out an equivalent fire. Somewhat in line with these figures are theprotected volume value relationship for the fluids. The estimatedprotected volume for was slightly over 40 percent greater than theprotected volume of carbon tetrachloride. The protected volume of thefluids containing methylene dichloride was slightly over 30 percenthigher than carbon tetrachloride. In the practical tests, carbontetrachloride extinguished the fires 50 percent of the time whereas theinventive fluids, which differed very little from one another in thischaracteristic extinguished the fires from 72 to 100 percent of thetime.

Thus it is seen that a fire extinguisher fluid has been provided whichfar surpasses the conventional fire extinguisher fluids, particularlycarbon tetrachloride, in use.

From the foregoing it will also be seen that this invention isrone welladapted to attain all of the ends and objects hereinabove set forthtogether with other chlorobrorno methane or ethylene dibromide does notexceed 30 percent. An example of such a percentage varied compound,again employing methylene dichloride and ethylene dibromide, consistsof, by volume, 10 percent ethylene dibromide, 15, percent methylenedichloride, 40 percent perchloroethylene and 35 percenttrichloroethylene. This compound has an empirical extinguishing numbervof 11, a liquid volume of 22.6, a i 514, and a relatively low cost atpresent prices. I

From the liquid volume values for the fire extinguisher fluids, it wasestablished that carbon tetrachloride is six to seven times more toxicthan the new formulations. From the practical test data, it was shownthat the new fluids are up to 50 percent better asextingu'ishing agentsthan carbon tetrachloride. The empirical extinction number data alsoindicates essentially the same advantages which are obvious and whichare inherent to the compounds.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth is to be interpreted as illustrative and not in alimiting sense.

Having thus described my invention, I claim:

1. A composition adapted for use in extinguishing fires composed of, byvolume, perchloroethylene in a ratio of not less than 30% nor greaterthan 40%, trichloroethylene in a percentage not less than 35 nor greaterthan 40, and chlorobromomethane in a percentage not less than 20 norgreater than 35.

2. A composition adapted for use in extinguishing fires composed of 40%trichloroethylene by volume, 40% perchloroethylene by volume, and 20% byvolume chlorobromomethane.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Industrial Solvents-Mel1an; Reinhold Pub. Co., N.Y., 1939;chapter 9.

fluids without methylene dichloride.

2. A COMPOSITION ADAPTED FOR USE IN EXTINGUISHING FIRES COMPOSED OF 40%TRICHLOROETHYLENE BY VOLUME, 40% PERCHLOROETHYLENE BY VOLUME, AND 20% BYVOLUME CHLOROBROMOMETHANE.